In order to provide colouring agents for keratin fibres, in particular for human hair, a person skilled in the art is aware of various dye systems depending on the demands placed on the colouring. What are known as oxidation dyes are used for permanent, intense colourations having appropriate fastness properties. Such colouring agents usually contain oxidation dye precursors, so-called developer components and coupler components, which create the actual dyes among each other under the influence of oxidising agents or atmospheric oxygen. The oxidation dyes are exemplified by excellent long-lasting dyeing results. Besides colouring, the lightening of the natural hair colour or bleaching is a very specific desire of many consumers. To this end, the natural or artificial colourants colouring the fibres are usually oxidatively decolorised with the use of appropriate oxidising agents, such as hydrogen peroxide. For temporary dyeing, dyes or toners which contain what are known are substantive dyes (direct dyes). These can be used likewise together with oxidising agents in lightening colouring agents.
In order to develop optimal dyeing power, oxidative dyes generally require an alkaline pH value for the colouring, in particular between from about pH 8.5 and about pH 11.5. For reasons of stability, oxidative dyes are usually produced only just before application, by mixing a dye component (agent for oxidative hair dyeing) and an oxidising agent composition. The dye component usually has an alkaline pH value for stabilisation of oxidation dye precursor products, and the oxidising agent composition usually has an acidic pH value for stabilisation of the oxidising agent, whereas the ready-to-use mixture should have an alkaline pH value so as to enable good penetration of the dye precursor products and the oxidising agent into the keratin fibres.
In addition, the application period for satisfactory dyeing results is usually between from about 10 and about 60 minutes. The ready-to-use colouring agent should therefore be formulated and packaged such that the colouring agent on the one hand can be easily distributed over the keratin fibres to be dyes, but on the other hand remains in the fibres to be coloured during the application time. To this end it is advantageous if the colouring agent has a certain viscosity which makes it possible to apply the agent, but which also leaves the agent behind at the site of use. This viscosity can be adjusted by polymer thickeners in the ready-to-use colouring agent, wherein this thickener can be contained both in the dye component or the oxidising agent composition.
The aforementioned oxidising agent compositions and dye components are usually incorporated into a cosmetically suitable carrier, such as a cream. The carrier ensures the above-mentioned homogeneous distribution and a sufficient residence time of the hair colouring agent on the hair.
A disadvantage is the complex production of a cream of this kind. A lot of energy is required for the melting of the fat components and the emulsification. The subsequent cooling consumes large amounts of cooling water.
Due to high fat components in conventional creams, continuous production can be implemented only with difficulty. Here, the constituents in the melt must be provided in such a ratio to one another to ensure pumpability.